The invention relates to a gas bag for protecting occupants in motor vehicles.
In the current gas bag designs, several flat pieces of fabric are connected with each other by one seam or several seams. During the unfolding process, the seams are exposed to a high tensile stress. Through this tensile stress, the seam holes which are pierced into the fabric pieces are widened. At the widened seam holes, hot filling gases escape, which result in a thermal stressing of the fabric pieces and of the sewing thread. Pressure losses owing to the outflow of gases through the widened seam holes must be compensated by corresponding dimensioning of the gas generator. These shortcomings of conventional gas bag designs were accepted hitherto, because seam connections are suitable for ensuring, with a low technical expenditure, reproducible characteristics over a large temperature range of xe2x88x92400xc2x0 C. to +105xc2x0 C. and over a period of up to 15 years. Also the recycling characteristics of the conventional gas bag designs are favorable.
The present invention provides a gas bag for occupant protection in vehicles, in which with a small additional expenditure the outflow of gases at the seams is largely prevented. According to the invention, along the seam at least one strip of sealing material is arranged, sealing the seam. The sealing effect which exists by means of the sealing material strip prevents gas from escaping in particular in the areas of the seam holes, because these are closed by the sealing material. The substance which is used as a sealing material must be sufficiently heat-resistant and in addition flexible, so as not to impair the folding- and unfolding characteristics of the gas bag. In advantageous embodiments, the sealing material is a substance based on synthetic polymer or silicate. The sealing material strip can be provided as a gas-tight band which is bonded to at least one of the fabric pieces. In the preferred embodiment, however, the sealing material strip is formed from a liquid or pasty material which is preferably applied onto the fabric pieces by a printing method. The application of the substance by means of offset printing is particularly expedient, in which the liquid or pasty substance is scraped on using a screen structured in correspondence to the shape of the seam.